Project Summary The proposed application focuses on the development of a plug-and-play living human kidney-on-chip for assaying secretion of drug candidates by the kidney proximal tubule. Once commercialized, the chip will enable drug developers to better screen pre-clinical drug candidates for nephrotoxic side effects. This stands to reduce the high attrition rate of drugs in clinical trials, given that about 20% fail because of nephrotoxicity, and would make drug development faster, more cost efficient, and safer. Conventional preclinical models are of limited use for assessing tubular secretion. In animal models, transporter proteins in the kidney epithelium differ significantly from those present in human kidney; 2D in-vitro models, even when using human cells, fail to provide appropriate culture conditions that enable appropriate cell function. The proposed kidney chip will leverage the commercially available Nortis organ-on-chip platform that is currently in use for a number of organ applications--including a first-generation kidney model that contains a human kidney proximal tubule, tissue-engineered from primary cells. In order to make the kidney chip useful for wide-spread use in pre-clinical assessment of renal secretion, substantial improvements are necessary. A marketable product requires a stable source of cells with sufficient performance, precision delivery of compounds to the basolateral side of the proximal tubule in the chip, and precise fluid sampling from the chip. Further, chips arriving pre-loaded with living proximal tubules will represent a significant value increase to the customer. Phase I of the project will aim to demonstrate that specific transporter proteins OAT1/3 and OCT2, which are crucial to renal secretion, function correctly (Phase I/AIM1). To prove this, proximal tubules in the chips will be exposed to specific substrates (adefovir for OAT1/3, cimetidine for OCT2), in conjunction with specific inhibitors of these transporters (para-aminohippurate for adefovir and metformin for cimetidine). The cells used for growing the tubules will be derived from an immortalized human kidney proximal tubule cell line that has been shown to express OAT1/3 and OCT2 in the correct cell compartments when cultured in the Nortis chip. Phase I/AIM2 will be to implement chip features for precise sampling of microliter-scale fluid volumes upstream and downstream of the tubule, which is required for assessing the secretory flux parameter termed the permeability-surface area product (Pa). During Phase II the chips will be equipped with features for tight control of compound delivery to the basolateral side of the proximal tubule (Phase II/AIM1). The following aim (Phase II/AIM2) will then focus on qualifying assays of kidney proximal tubule secretory clearance for OAT1/3 and OCT2 with sufficient statistical power to establish robustness and reproducibility. Phase II/AIM3 is designed to establish that living kidney chips can be shipped to customers with uncompromised assay performance, which will be validated by an independent laboratory. Once fully developed and commercialized the proposed kidney chip might be suitable for applications beyond the pharmaceutical sector, such as environmental health & safety, precision medicine, and regenerative medicine.